An X-ray inspection apparatus is widely used for non-destructive inspection of a semiconductor product and the like. For example, in inspection of the presence or absence of internal defects of a semiconductor component such as an integrated circuit (IC) mounted on a printed board, an inspection target is irradiated with X-rays such that an X-ray fluoroscopic image is captured, and the quality of a product is determined on the basis of the X-ray fluoroscopic image.
In a case where an inspection target is small, such as a semiconductor product on a printed board, it is desirable to perform inspection by capturing an enlarged X-ray fluoroscopic image. Therefore, inspection is performed by using an apparatus in which a two-dimensional X-ray detector is disposed to face an X-ray generation device irradiating a cone beam-shaped X-ray, an XYZ stage which is movable in a three-dimensional direction is disposed in an inspection space therebetween, an inspection target object is placed thereon, an observation position is defined by moving the placed inspection target object in XY directions, and an observation region can be enlarged and reduced by moving the inspection target object in a Z direction.
However, since radiation resistance design is not applied to a general semiconductor component, there is a case where electrical characteristics are changed due to the influence of X-rays applied during X-ray inspection, and thus the semiconductor component is damaged.
Since it is known that such a problem depends on a cumulative irradiation dose of X-rays applied to an inspection target object, a cumulative irradiation dose value of X-rays applied to an inspection target object is managed through expectation or measurement.
For example, in an X-ray inspection apparatus provided and used in a mounting assembly line for a printed board, in a case where a plurality of semiconductor components are placed to be dotted at positions separated from each other on a printed board, a method may be used in which an X-ray irradiation region for the printed board is divided into small regions, and imaging is performed a plurality of number of times while allowing irradiation regions to partially overlap each other. In this inspection, an X-ray irradiation scheduled dose value per component is calculated on the basis of position data of a mounting component and an X-ray irradiation dose value for each X-ray irradiation region, and is not made to exceed an X-ray irradiation allowable dose value through comparison with the X-ray irradiation allowable dose value per component (refer to JP-A-2002-350367).
A method is disclosed in which a printed board is placed on an observation table of an X-ray inspection apparatus, a position and a height of a stage are adjusted such that a position of an inspection target object is located between an X-ray source and an X-ray detector, and a cumulative irradiation dose of X-rays in the inspection target object is managed in the following method (refer to JP-A-2011-179936).
In other words, prior to inspection, reference X-ray conditions (a tube current, a tube voltage, a distance from the X-ray source to the observation table (hereinafter, referred to as an “SOD”)) are set in advance, and a dosimeter is disposed on the observation table so as to measure a dose rate which is then stored in a control section. During inspection, an inspection target object is placed on the observation table, the observation table is moved, X-rays are applied at a desired position, and an X-ray fluoroscopic image is captured and is displayed on a display. Next, X-ray conditions (a tube current, a tube voltage, and an SOD) during X-ray irradiation are recorded, and an irradiation time is measured, and a dose rate in these X-ray conditions is calculated on the basis of a dose rate under the reference conditions stored in advance.
Specifically, since it is known that a dose rate is proportional to the square of a tube voltage, proportional to a tube current, and inversely proportional to the square of an SOD, the dose rate is calculated on the basis of a dose rate under the reference conditions by using set conditions of a tube voltage, a tube current, and an SOD. A product between the irradiation time and the dose rate until the X-ray conditions are changed is calculated, and thus an irradiation dose in the inspection target object is obtained. The same computation is performed under changed X-ray conditions whenever the X-ray conditions are changed for the same inspection target object, and an irradiation dose is added, so that a cumulative irradiation dose from starting of X-ray irradiation is computed (refer to JP-A-2011-179936).